Recording system



y 1953 A. HOLCOMB 2,639,965

RECORDING SYSTEM Filed March 11, 1952 2 Sheets-Sheet 1 J'WEEP CIRCUIT 40 RATE or Ms:

CONTROL ADD/T/VE 45 4/ C/RC U/ T ,r p p TRIGGER 36 c c C/RCU/ T 1 (yo 34 1. J THRESHOLD M CONTROL THRESHOLD S/GNAL C m6 0/ T comer T/ON (REC T/F/ER CIRCUIT ,.J 41 3 57 1- SIGNAL j l f 44 a3 INPUT SWEEP ARMS T 5 6 5 2a 7 lNDUCT/VE PULSE FROM SWEEP ARMS a 7 COMB T 4 1 r PILOT GENERATOR VOLTAGE PLAT/5N T PAPER DR/l E O /5 P, OR 3 /7 RECORD PAPER /5 i CONTROL I /& SUPPLY M J CAB/NET CONTROL FIELD H ARMATURE 1 I r" w. I

FIG. 5

*- C HART AREA MECHANICAL SWEP --f ll TRIGGER THRESHOLD oooooooooooooooo //V l/E/V TOR S/GNAL I A L. HOL COMB RANGE I B) E ATTORNE V May 26, 1953 A. HOLCOMB 2,639,965

RECORDING SYSTEM Filed March 11, 1952 2 Sheets-Sheet 2 rmmmlww uuuuull l w F/G.3 5 6 5 2a /0 f l} l6 /7 2/ /a II F 1 HI T NT"" W WW p i V "u J FIG. 1

6 (a) (I) YURI [HF] HFIHHH l moras-mrm LJLILILJLILJLJLJLJLJLL VOLTAGE (1,) ADJUSTABLE FOR CALIBRATION -4 4---$WEEP van-4a:

(c) MECHANICAL SWEEP BEG/NS x I MECHANICAL SWEEP ENDS 4 x j t .4 rR/cam THRESHOLD /NV/VTOR smms A.L.HOLCOMB BY (a) I Mm Patented May 26, 195?;

RECORDING SYSTEM Arthur L. Holcomb, Tarzana, Calif., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 11, 1952, Serial No. 275,951

7 Claims.

This invention relates to high speed chart recorders, and particularly to recorders using an impulsive, or spark, discharge.

The object of the invention is apparatus for recording at high speed by means of an impulsive, or spark discharge, the successive magnitudes of an electrical signal.

A feature of the invention is the association, with a multiplicity of conductors in constant contact with the recording surface, of rotary distributor arms to direct the impulsive electrical discharge to the recording surface.

Another feature of the invention is the generation of a saw-tooth voltage wave synchronized with the motion of the rotary distributor arms, which is combined with the signal voltage, so that, at some time during the travel of a distributor arm across the multiplicity of conductors, the combined saw-tooth and signal voltages will exceed a threshold value.

A further feature of the invention is an electrical trigger circuit, energized when the combined voltages exceed the threshold value, to release suflicient stored electrical energy to bridge the short gap between the distributor arm and the nearest conductor and thus to supply sufficient current to mark the recording surface.

The recording surface is preferably a known type of electrosensitive chart paper which is discolored by the passage of an electrical current therethrough and forms a permanent record without further processing, though other types of electrosensitive materials may be used.

In the operation of this recorder, electrical pulses of steep wave front are recurrently generated in synchronism with the mechanical position of a constantly rotating shaft. These pulses initiate the generation of sweep voltages, which rise at a uniform rate, and, through predetermined arcs of rotation of the shaft, are proportional in amplitude to the position of the shaft. These recurrent sweep voltages are superposed on the signal voltage to be recorded, and the combined voltage supplied to a trigger circuit having a well defined threshold voltage. When the combined voltages exceed the threshold voltage, the trigger circuit is energized to control the generation of an electrical impulse of short duration. An arm, driven by the shaft and synchronized in position in relation to the initiating pulses, sweeps at uniform speed past the ends of a line of conductors located near the chart. The distance moved by the arm along the line of conductors is proportional to the amplitude of the sweep voltage. The impulsive discharge produces a spark between the arm and the end of the nearest conductor, causing a current to flow in the conductor and mark the record, thus, the distance traveled by the arm over the ends of the conductors between the initiating pulse and the discharge is proportional to the amplitude of the signal voltage.

In the drawings:

Fig. 1 shows, in partial block schematic, a typical embodiment of the invention;

Fig. 2 shows a top view of the motor driven recorder;

Fig. 3 shows a side View in part section, of the motor driven recorder;

Fig. 4 depicts the type of record made by the recgrder, distorted in scale to show the marks; an

Figs. 5 and 6 are plots of the voltage waves used to produce the record.

The motor I, mounted on any suitable base 2, should be a constant speed motor, and may conveniently be of the type described in my article Precision Speed Control published in the Journal of the Society of Motion Picture Engineers, volume 52, May 1949. The associated control circuit is mounted in the control cabinet 3. An insulating support 6 is mounted on the shaft 4 to retain the distributor, or sweep arms 5, 5. If desired, suitable gearing, not shown, may be interposed between the motor shaft and shaft 4. With direct drive and a, motor speed of 10,000 revolutions per minute, six distributor arms 5, 5 equally spaced at Gil-degree intervals may be used, and each arm 5 will then sweep over an arc of degrees in 1 millisecond. A conductive sleeve 1, insulated from shaft 4, contacts all of the arms 5, 5. A slip ring, or other suitable contactor, connects the sleeve 1 to the recording circuit.

The shaft 9, journalled in the supports it, ll, is geared to the shaft 4, and drives shaft l2, journalled in support l3. The chart paper I6 is led over a smooth conductive platen 2U, supported by a suitable bracket 2|, to the take-up reel [8. The chart paper 16 is advanced in synohronism with the movements of the arms 5, 5 by the sprocket l5, geared to the shaft l2, and journalled in supports l4, [6. The take-up reel i8 may be driven in any desired manner. While one operative embodiment of the invention has been disclosed, it is evident that many changes in mechanical details may be made within the scope of the appended claims.

Associated with the motor described in my above-mentioned article is a pilot generator of the inductor type, which is used to sense changes in the motor speed and to activate the control circuit to correct any tendency of the motor speed to change from the assigned speed. The number of distributor, or sweep arms 5, 5 may be made the same as the number of poles on the pilot generator, so that the phase relation of the amplitude of the generated voltage to any point on the active arc of rotation of the arms 5, 5 will be constant. At a speed of 10,000 revolutions per minute, a six-pole inductor generator will deliver an essentially square Wave having a repetition frequency of 1,000 ycles per second, and each arm will sweep over a Gil-degree arc in one cycle of the generator voltage, The length of the sweep arms is selected so that the desired chart width is approximately equal to the chord of a 60-degree are near the tips .of the arms, thus, each arm will sweep across the chosen chart width in one millisecond, and the beginning of the sweep over the chart width may be made to eoihoi e w th so desi e point on the seniet ti olta e Were.- The i ot ener to vol a e u hsv he u d t initiate o terminate on elseroh e es ioh v ioh is d rect iuhst oh. o the weep ei h posi i n with PQ to he reco derh n us n othe trees o c nstan pee motors not ed wi h oi ot seh rs ors, inductor coil 22 may be located so as to be inlu h e hr the 5 5 to roduce a indu tits pulse With the. passa e o 'o eh arm- The martinis? oi he e ee ose s ive oh r pap it is controlled by a large number of electrical seme ters ihsuls o i oih seh ther moun ed with one end in contact with the paper, the oth r ne o these c ndu tors receiv n e e ti'ieal imou ses from he rms 5. which ass through the conductors and paper to the platen 2%- As shown ii the a er I i th marked in steps which are a function of the hum? h and site o t e conductors Us n a fou 's h idth of esold. iQl h assure-or of o equartel' her se t. the s eps. between. ma ks. must n t. he m r thee .110 inch. and. as. eohduoti h m y oooui i t o seisoeh conduc ors, the maximum iam ter o a condu tor w th nsulation m ot h more than -.00. nch wh ch is .200. eoniuoto s. he ihoh. or 8.00. c nductors lfor a fourinch record.

hi ne end. of hes conducto s s in c nta Wit he Panel and ma be ubject t som a ras 9. 1 th eo e ue o s. m h mad ofsome. subtance wh h. res ts. abrasion. uch a o e of the Well-known a o of n ck l and. iron.

A nickel-iron wire insulated with a heat resists t inso eine. ename su h as an namel o ts hihe s io he. is closely Wound. in a. helix over a lev of sless loth o rin a. smoo h cy i der- When. the. e th. of the hel x. quals, th width of the d ire so d he Wir is. tied down, dipped i a heat resist nt. t e mosett ne arnish. su h s s io he va ni h. a d li htly baked. This pp n is. rep ated. until the wires. are well bonded to the glass. cloth and to. each other. outer layer of glass cloth is then w d o r th ssembl i h. t e. o n of. th outer layer of glass cloth coinciding with the joint of the inner layer, and the dipping in nam a d. sk he. r peated u i a a is ctory assembly is produced. The coil is then slit length wise at the joints, in the glass cloth, peeled off the cylinder, and cut into proper lengths.

The lower end of an assembly 0,15 conductors, or comb, 23 is clamped or molded in an insulating clamp 24, made of some good insulating ma: terial which is dimensionally stable and mechanically rugged. The upper end of the comb 23 is similarly clamped in a clamp 25, made of similar material and shaped to the contour of the movement of the arms 5, 5. The clamps 24, 25, may then be ground accurately to the desired shape. A support 26 unites the clamps 24, 25 and may be designed to allow sufiicient slack in the comb 2-3 to permit independent adjustment of either of the clamps 24, 25. The complete assembly is supported by a bracket 21, secured to the platen 20, or support 2|, and attached to the clamp 2.4. If desired, a spring may be embodied in the bracket 2"! to press the clamp 24 against the pape 16- If each of the arms 5 sweep across the comb 23 in one millisecond, signals varying in amplitude at rates up to 100 cycles per second may be accurately recorded. Unidirectional signals may be supplied directly to the recording circuit, but modulated high frequencies must be rectified to produce a voltage varying with the amplitude of he env l pe oi e m dulated currents. The modulated signal waves may be supplied to a. signal rectifier network 30, the rectified pulsatcurrent flowing to ground through resistors 4. 35, a ca ac to 33 m hs the ctifi d current.

The pilot generator voltage, or the voltage indueed the ductive coi 2 is supplied to a sweep circuit 49, of known type, to initiate a how o c ren th o h es s o s 35.

h pilot generato volta W ve is shown in i 4*. nd the s ee v ta av in Fi e 6 The swee v l a e rises u t l the sudden ha e toward ne a iv the p l t vol as at 1/. terminates he ri of he swe p vo ta a d uo s his volta e to zero. Wh n the p o o tage ceas s han n at a a id t in t e n gativ directi n. he swe p voltage a ain ises,- The current from the sweep circuit 40, flowing in esistor 35 combines wi h the r ct fied i na u l'ent. f ow g this resistor to produce a combilled v l e a r s resi to 35 as sh wn in Fi 6c.

The. imple additiv c cuit. formed f resi tors 36.. 3. 36, m y if desired, b r placed by a sum.- e mplifi r. such. as t amplifier shown in United Stat s Pa e t A01jl79, June. 11, 1946, K- D-. SWartz l. Jr.

The ummation vo ta e developed across. resistor 3 is supplied o a kno tri e circuit 4.4. ha in a, th esh ld ontrol adju ted so that the circuit will not operate until the applied voltage t e th esho d. a e

Th add ti n o th i na olt e to the sw ep olt e roduc a i dis o ti n. f the shape r he. ee a e wav o tha en the. sin:-

vol oe i e'. the ombined. Wave shone. ends o h ooh sv do nward. and when the gna volta e, is fall the m ined wa shone ten t he on x. wa d. This d sto tion may ter t point at. io t e amp itude f the combined wave exceeds the threshold voltage of he. ig u nd m y produ e an err r in the record. This error will be proportional to the rat of an of gnal voltage. and ma use l t r r g on on n reas n sixhs and e ly tri ger n n a decr as si nal.

he ol a o s e om i ation of a. re.- sistor in series with a capacitor is proportional to the rate of charge or discharge of the capacitor; and changes. in polarity with the charge or dis, charge, thus, such a circuitznay be used to correct the, e r r i response of. the tr g er, circ it.

A portion oi th tified signal voltage. is, supplied to the serial combination of resistor 42 and capacitor 43, and the voltage drop developed across resistor 42 is applied as a correction voltage to the threshold control element of the trigger circuit 4!. A resistor M, or other attenuating means may be shunted across this threshold correction circuit to vary the amplitude of the corrective voltage.

The trigger circuit produces a series of pulses, as shown in Fig. 6d. These pulses trigger the bistable, or flip-flop, circuit 45, which in turn triggers alternate sections of the reactive storage and discharge circuits No. 1 or No. 2. Alternate functioning of the two similar sections is desirable in order to permit a relatively long charging time for each section.

In the reactive discharge circuit shown in circuit No. l of Fig. 1 capacitor 50 is charged from source through rectifier 52 and resistor 53; and capacitor 55 is similarly charged through rectifier 55, and resistor 56. The grids of the grid controlled gas-filled tubes 5?, 58 are normally biased beyond cut-off, but when circuit 45 is first actuated, a positive pulse is applied to the grid of tube 5i, breaking down this tube and permitting capacitor 55 to discharge through ground, platen 25, paper i5, comb 23, arm 5, slip ring 8 and the anode-cathode path of the tube 5 1. Similarly, when circuit 45 is restored, capacitor 54 discharges through ground, platen 20, paper l6, arm 5, slip ring it and tube 58. The successive discharges produce small areas of discoloration in the paper is corresponding to the conductors in the comb 23 which are aligned with the arm 5 at the instant of discharge.

The discharge may also, if desired, be produced by inductive means as in circuit No. 2. Current from battery 50 flows through coil GI and tube 52; and through coil 53 and tube 64. Tubes 52, 64, are vacuum tubes biased to full conductivity. When circuit 45 is first actuated, a negative pulse is applied to the control grid of tube 62, cutting ofi this tube. The magnetic field of coil 6| collapses, causing a current to flow through capacitor 52, ground, platen 20, paper l6, comb 23, arm 5, ring 8, rectifier 65. Similarly, when circuit 45 is restored, tube 64 is cut off and coil 63 causes a current to flow through capacitor 62, ground, platen 20, paper 16, comb 23, arm 5, ring 8, rectifier 66.

Switch 69 may be moved to select the type of discharge desired. Typical sweep, trigger, and bistable circuits are described in the book Waveforms, volume 19 of Radiation Laboratory Series, published by lVlcGraw-l-lill Book Company, New York; and in the book, Time Bases, O. S. Puckle, published by John Wiley and Sons, Inc., New York.

The sweep arms 5 are shaped to form knife edge electrodes, or are equipped with replaceable knife edge electrodes, which clear the comb 23 by a few millinches. The impulsive discharge supplied to the arms 5 will break down this air gap to mark the record paper, and may also gradually burn away the sharp edge of the electrode. With a knife edge electrode, the active area may easily be renewed by a small axial adjustment of the knife edges along the arms 5.

If desired, the upper portion of the comb 23 may be shaped to produce other than a linear relationship between the sweeps of arms 5 and the record on paper l6. Logarithmic, exponential, sine, cosine, or other relationships may thus be produced.

By well-known means, the motor frame may be arranged for rotation through a small angle to accurately locate the arms 5 with respect to the synchronizing wave from the pilot generator; and means may be provided to adjust the comb 23 with respect to the arms 5 to make the sweep width correspond with the chart width.

Calibration With the unit operating, a measured direct voltage, having an amplitude equal to or greater than the maximum signal amplitude to be recorded, is applied to the signal input, and the threshold voltage adjusted until, as shown in Fig. 5, a mark is made at the left edge of the chart where the sweep voltage is zero. This direct voltage is then removed, the signal input left open, or short-circuited, to provide zero signal voltage, and the rate of rise of the sweep voltage adjusted until the chart is marked on the zero ordinate at the right edge of the chart.

To check the design or adjustment of the threshold correction circuit, a sinusoidal wave of cycles may be applied to the signal input. The arms 5 will make four complete sweeps over the comb 23 during one-half cycle of this wave, and the relative phase or this wave and the motion of the arms may be adjusted so that five marks are produced on the record for each half cycle, two marks at zero at the beginning and end of the half cycle, one at the maximum amplitude of the wave, and two at intermediate values. The intermediate values will respectively be on the rising portion of the wave, and on the falling portion of the wave, and should be equidistant between the maximum and a zero. The correction circuit may be modified or adjusted to produce this result.

What is claimed is:

1. In a recorder having a framework supporting a chemically prepared recording surface, a plurality of insulated conductors supported by said framework in alignment across the width of the recording surface adjacent to said surface, the free ends of said conductors being arcuately shaped, a rotatable distributor having a plurality of radially projecting conductive arms adjacent to the arcuate surface, the circumferential spacing of said arms being equal to the arcuate width of said conductors, motor means mounted on said framework driving said distributor, said means controlling the generation of an alternating pilot wave, a sweep circuit controlled by said wave to supply a continuously varying voltage to said distributor during the sweep of an arm across the conductors, and means connected to said distributor and controlled by the signal to be recorded to supply a succession of impulsive discharges to the distributor during the duration of the signal.

2. Recording apparatus including a framework supporting an electrosensitive recording surface, a plurality of insulated conductors supported by said framework in alignment across the width of said surface, each conductor having one end adjacent to said surface, a rotatable distributor having a plurality of radially projecting conductive arms sweeping over the free ends of said conductors, a motor mounted on said framework and driving said distributor at constant speed, a generator of recurrent voltage waves controlled by said motor to linearly vary during the sweep of an arm over said conductors, summing means for combining said recurrent waves with the signal voltage wave to be recorded, and impulse generating means connected to said arms and energized when said "combined -waves exceed a predetermined value to discharge a current through oneof said arms, the adj acent.-conductor, and the recording surface.

'3. The combination in claim- 2 "with means driven by said-motor'to advance the-recording surface at constant speed.

4. The combination in claim 2 in which the free ends of said conductors'aredisposedon an arc of a circle concentric with the center-ofirotation of said arms. V

5.'The 'combination'in claim 2 in which *the arms ai'edormedas-knifeedges facing saidconductors.

6."The combination in claim 2-in which-agenerator driven-by the-motor-controls the generator of recurrent waves.

ing conductive: arms sweeping j over: the free ends of said conductors, "a motor -mounted 2011 .said

framework and driving said distributor and'said surface t at constant* speeds, a a generator driven by saidf-motor to produce an-electrical pulse at -t;he"beginmng of each-sweep of an arm'across said conductors, a-sweep circuit controlled by said pulses to produce a voltage linearly rising at constant rate during 2 the sweep of an arm, lO-- for combiningsaid-sweep"voltage with the voltage to be recorded, a. trigger circuit connected to summing meanslconnected to said sweep circuit said summing means sand'energized when said combined voltages exceed-a predetermined value,

and -anj impulse generator connected from said trigger circuit to said arms and activated by the 'energizatien ofsaid'trigger circuit/t0 discharge an electrical impulseithrough one of said arms,

the adjacent I conductor .andthe 1 recording' surface.

ARTHUR L. HOLCOMB.

No references cited. 

